Current efforts emphasize the biology and pathogenicity of Mycoplasma species of humans and, where important, how mycoplasmas (or other mollicutes) from animals and other hosts play a role in human or other host infections. Further observations have been made on the role of mycoplasmal infections in immunocompromised patients, usually involving individuals with genetic immune deficiencies, or those patients who are receiving various immunosuppressive drugs because of organ/tissue transplants or treatment of malignant disease. We have now additional evidence of the important role that mycoplasmas of animal origin can play in such infections. Mycoplasma maculosum, an organism commonly found in the canine respiratory and genital tracts, was identified as the causative agent of meningitis in a child with hypogammaglobulinemia. Chemotherapeutic efforts, in the absence of the patient?s ability to mount some type of an immune response, have been generally unsuccessful, until a newer experimental antibiotic was used in prolonged therapy. These findings, and our previous identification of other feline or canine mycoplasma infections in immunocompromised patients, emphasize why all patients with such immune deficiencies should avoid close animal contact. Some recent studies using molecular probles suggest a role of mycoplasmas (especially Mycoplasma fermentans) in chronic fatigue syndrome (CFS). In a collaborative study, Mycoplasma genitalium has been isolated from the blood of a patient with this syndrome and the immunologic response of the patient and his wife indicate evidence of recent infection with the organism. Further work on the in vitro cytopathogenicity of the agent isolated is being investigated. We have recently identified two new, and previously unreported, Mycoplasma species from the respiratory tract of both desert and gopher tortoises in a collaborative study in Florida and California. The taxonomic characterization of these new organisms has allowed development of a variety of serologic and molecular techniques to rapidly identify the organisms and to study acquisition of infection, disease distribution, immunological responses, and other epidemiological features of a disease in an endangered species. Since many mycoplasmas or other mollicutes are difficult to grow in primary culture from host material and identification techniques are prolonged and involved, we are participating in a pilot study to evaluate the use of 16S rDNA sequence data as a rapid means of identifying Mycoplasma species of humans and animals, and a group of helical mollicutes (genus Spiroplasma). Full 16S rDNA sequences are now available on almost all of the 100 or more species in the genus Mycoplasma. Sequence data on 10 Spiroplasma species, available from our earlier collaborative study on the phylogeny of these organisms, have been combined with sequence analysis from another 38 currently defined Spiroplasma species to provide a comprehensive file to evaluate the practicality of this reference to provide rapid species identification. The phylogenetic relationships are closely correlated with previous classifications made on genome characteristics and serologic patterns. This activity is one part of a collaborative program to develop a multiple organism microbial identification project.